In the production of industrial plants for bottling liquids or for packaging items of various kinds, the design of appropriate systems for transferring the products from one processing station to the next and toward the store is extremely important.
In carrying out the production cycles performed by these plants, it is often necessary to convey and stop the conveyed products in chosen positions, so that it is possible to perform the various steps provided by said process, such as for example filling bottles, closing them, or packaging products of various kinds.
Conveyor chains of a known type are currently used to transfer items within plants in which the operating cycles entail conveying or stopping said products in one or more positions; said known chains are composed of a plurality of links, which are mutually connected so as to form a chosen path, which can comprise straight and curved portions.
One particularly felt requirement is to allow to stop the products in the chosen positions without requiring simultaneous stopping of the conveyor chain, which would entail very complex execution and high operating costs thereof.
For this purpose, it is known to provide conveyor chains that are constituted by interconnecting a plurality of links, each of which comprises a base body that has a substantially rectangular plan shape, on the transverse sides of which one or more shafts are supported, said shafts being arranged longitudinally with respect to the base body and transversely to the direction along which the products advance on said chain, a plurality of rollers being freely rotatably associated with said shafts and constituting the upper conveyance surface of the chain.
In a first known type of link, on the transverse sides of the base body there are a plurality of receptacles, which are approximately U-shaped and open upward, for supporting the one or more shafts, the ends of which are inserted from above into said receptacles.
In a second known type of link, at the transverse sides of its base body, there are a plurality of through holes, which are for example aligned in pairs and within which the ends of the one or more shafts are inserted, being thus supported.
In both of these known kinds of embodiment, if the products to be transferred have considerable dimensions and/or weights, the shafts, in view of their longitudinal extension, are made to rest, in one or more of their intermediate points, on a corresponding number of supports, which protrude upward from the base body and have a receptacle for rotatably accommodating a portion of said shaft.
The presence of the rollers in these known types of link allows both to entrain the products and to stop them without having to stop the movement of the conveyor chain.
The transferred product can in fact be locked in the intended position by means of a retention barrier, without generating intense friction with said chain, by way of the interposition of the rollers, which by rotating about the shaft that supports them reduce drastically said force; in this manner, the presence of motionless objects on the chain does not constitute a hindrance to the travel of said chain.
The main drawback that can be observed in these known types of conveyor chain is the fact that they have an intense wear of the intermediate supports, since the shaft that rests on them in an upper region, if turned by the rollers that it supports, slides continuously on said intermediate supports even in the presence of lightweight loads on the conveyor chain.
Another drawback of known types of conveyor chain is that since each shaft rests directly on the corresponding intermediate support, it is extremely difficult to clean said region of the conveyor chain, and therefore debris that arrives from the outside environment or from the conveyed products, such as for example dust or splinters from the breakage of glass bottles, may jam between the shaft and the intermediate supports, increasing resistance to the advancement of the chain and making it wear faster; accordingly, long line downtimes are needed to perform the necessary cleaning operations.
Another drawback of these known types of conveyor chain is that at the intermediate supports there is a considerable discontinuity in the upper supporting surface, which may give rise to imperfect placement of the product on said chain, especially when it has a small contact base, consequently hindering the correct execution of the cycle of the plant within which said chain is inserted.